JVL MIS17 Series User Manual page 301

11.7 More details of CANopen Theory
Read PDO service:
The read PDO service is an acknowledged service. One of the several PDO consumers
send an RTR message to the network. After it has received the RTR message, the PDO
producer sends the requested PDO. This service is used for RTR queries. Using this ser-
vice, an actual value can be interrogated independently of the selected cycle time. The
following figure shows a read PDO service:
PDO identifier:
In the CANopen profile, it is only possible to have four transmit and four receive PDOs
enabled at the same time. In the MIS motors (or SMC66/85), all PDOs are disabled when
the module is booted up. The user must choose which PDOs the application will use and
enable these.
The PDO configuration can be seen either in the EDS-file or in the CANopenExplorer
program, where the communication and the mapping parameters are shown.
There are two standard methods to map the PDOs in CANopen: static mapping and dy-
namic mapping. In static PDO mapping all PDOs are mapped in accordance with some
fixed, non-modifiable setting in the relevant PDO. In dynamic PDO mapping, the setting
of a PDO can be modified. It is also allowable to have a flexible combination of different
process data during operation.
11.7.4 SDO (Service Data Objects)
SDO: can access all entries in the object directory but they are normally used in the ini-
tialization during the boot up procedure. Some SDOs characteristics are:
- Confirmed transfer of objects
- Data transfer/exchange is always non-synchronous
- Values greater than 4 bytes are transferred (Normal transfer)
- Values not more than 4 bytes are transferred (Expedited transfer)
Basically an SDO is transferred as a sequence of segments. Prior to transferring the seg-
ment, there is an initialization phase where client and server prepare themselves for
transferring the segment. For SDOs, it is also possible to transfer a dataset of up to four
bytes during the initialization phase. This mechanism is called an expedited transfer.
Download SDO protocol:
The download SDO protocol is used to write the values of the object directory into the
drive.
JVL Industri Elektronik A/S - User Manual - Integrated Stepper Motors MIS17x, 23x, 34x, 43x
PDO Producer
Indication
Response
TT1087GB
0 L = 0....8
Proces data
PDO Consumers
Request
Confirmation
301